This section provides background information related to the present disclosure which is not necessarily prior art.
Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. The removal is achieved by dissolving air in the water or wastewater under pressure and then releasing the air at atmospheric pressure in a flotation tank or basin. The released air forms tiny bubbles which adhere to the suspended matter causing the suspended matter to float to the surface of the water where it may then be removed by a skimming device.
Dissolved air flotation is very widely used in treating the industrial wastewater effluents from oil refineries, petrochemical and chemical plants, natural gas processing plants, paper mills, general water treatment and similar industrial facilities. A very similar process known as induced gas flotation is also used for wastewater treatment. Froth flotation is commonly used in the processing of mineral ores.
The feed water to the DAF float tank is often (but not always) dosed with a coagulant (such as ferric chloride or aluminum sulfate) to flocculate the suspended matter.
A portion of the clarified effluent water leaving the DAF tank is pumped into a small pressure vessel (called the air drum) into which compressed air is also introduced. This results in saturating the pressurized effluent water with air. The air-saturated water stream is recycled to the front of the float tank and flows through a pressure reduction valve just as it enters the front of the float tank, which results in the air being released in the form of tiny bubbles. The bubbles adhere to the suspended matter, causing the suspended matter to float to the surface and form a froth layer which is then removed by a skimmer. The froth-free water exits the float tank as the clarified effluent from the DAF unit.
Some DAF unit designs utilize parallel plate packing material, lamellas, to provide more separation surface and therefore to enhance the separation efficiency of the unit.
DAF systems can be categorized as circular (more efficient) and rectangular (more residence time). The former type requires just 3 minutes; an example is a Wock-Oliver DAF system (www.wockoliver.com). The rectangular type requires 20 to 30 minutes; a typical example is a Syskill DAF system (www.syskill.com.au). One of the bigger advantages of the circular type is its spiral scoop. A typical DAF system is shown in the schematic diagram of FIG. 13.
The DAF Corporation (www.dafcorp.com) FC Maximizer clarifier is designed and manufactured for harvesting algae. It is a hybrid DAF clarifier. Algae feeds on carbon dioxide and sun light. Algae's biomass once refined can be used for animal feed or its lipid oil for blended petroleum based fuels. The FC Maximizer clarifier is a cost-effective way to harvest algae. It can also feed algae. Part of the FC Maximizer clarifier system is the AMT air dissolving system. It can be used to nourish algae with a side stream of CO2 as a nutrient. This side stream of carbon dioxide with laden water and compressed air from this AMT is injected into the FC Maximizer clarifier as fine micron bubbles. These micron bubbles rise to the surface of the water in the tank at a rate 10″ to 12″ per minute. Hundreds of millions of all equal sized, fine micron bubbles entrap themselves in the suspended solids or algae bloom in the FC Maximizer tank.
Parallel with this process, on the open tank top rim is a rotating stainless steel tank carriage that supports the fixed and rotating tank internal parts. A stainless steel, variable speed, two blade rotating scoop is attached to it. Again, this design gently dips and scoops up the dense fine float mat and discharges it into a holding tank. Clean carbon dioxide enriched nutrient water is discharged from the clarifier tank. This water can be piped back into different systems for a multitude of uses.
The FC Maximizer clarifier is self-cleaning. It operates with minimal turbulence in a shallow round tank. The FC Maximizer clarifier will remove 98% of the algae bloom and lipid oil within the first two and a half minutes. The clarifier's wetted parts are all stainless steel. Sizes ranging from 20 gpm up to 9000 gpm are manufactured.
However, the prior art does not directly remove algae from open bodies of water on an in-lake basis utilizing dissolved air floatation technology.